If I get any fatter, I'll have to cut down on art. Tight spots seem to be in. A couple of months ago, at the Tate Liverpool, I got stuck in the narrow opening of a walk-through sculpture - aptly titled
Isthmus - for long enough to imagine the humiliation of being soaped out by gallery staff.

If I get any fatter, I'll have to cut down on art. Tight spots seem to be in. A couple of months ago, at the Tate Liverpool, I got stuck in the narrow opening of a walk-through sculpture - aptly titled
Isthmus - for long enough to imagine the humiliation of being soaped out by gallery staff.

And access to the main galleries at the Royal Academy isn't much easier. The visitor is admitted through a small, low and awkwardly angled trapdoor, and I wasn't sure I was going to make it. (An alternative route is available, if you insist.) Inside you find yourself in the first work - a dim, cramped, mazy and delapidated cellar environment, which you must scramble through. You have just entered Apocalypse.

Apocalypse: Beauty and Horror in Contemporary Art opens tomorrow. It's an international group show, with work by 15 artists - some famous, like Jeff Koons, some not, like Gregor Schneider the cellar-maker. And like many contemporary group shows, it comes framed with a slightly pretentious curatorial concept. Or rather, more than slightly pretentious - extravagantly pompous. Perhaps that is not as obvious as it should be.

I mean, when Coppola called his film
Apocalypse Now, it was clearly a vainglorious gesture, and it was no surprise that the film went the same way. And when you come across a contemporary art exhibition called Apocalypse, you have to wonder. Is it a kind of joke? Is it just crass? Or what is it?

Yet I see that this line of questioning betrays my assumption that visual art will operate more intelligently or more scrupulously than Hollywood - and that is probably wrong. Like everything else, visual art now arrives in a cloud of mood-making where disbelief is entirely suspended. Apocalypse. New Millennium. Beauty. Horror. Extremity. Catharsis. Sounds big, sounds fun. Don't think, gape. So you may say: just ignore the publicity and cut to the contents. I will. But the publicity is important. The publicity comes first. Without the publicity, the exhibition (which this newspaper is supporting) wouldn't exist.

With Apocalypse, the RA wants to do a repeat performance of Sensation three years ago - another high-profile, cutting-edge contemporary art show - with repeat box-office, too. But notice the difference. Sensation didn't need a theme. It was based on an existing fact - the indisputable success story of Young British Art. Apocalypse has no such basis. It has to establish for itself an equally grabbing image and identity out of the air. And I suppose grabs don't come much more powerful. The End of the World: everyone likes that. It may mean nothing, but it should get them in.

Once in, though, it's another matter. Going through the show, you do naturally start by trying to match the contents with the concept. But it becomes clear very soon that this approach just isn't going to work. Theme and show are two quite different things - indeed, the discrepancy is rather wider than with most theme-shows.

Apocalypse is simply an arbitrary mixture of contemporary art. It certainly includes work with (loosely speaking) apocalyptic tendencies, but then so would any such mixture. It doesn't have a higher than average proportion. I doubt whether someone visiting it blind would deduce its supposed agenda.

So start again. Put the Last Things out of your mind. Don't go expecting the Book of Revelation. And don't go either expecting - what seems also to be promised - a knock-down sequence of the flash and the aggro. There's a bit of that, yes, but it's leavened with a good helping of the dull and the null, and one or two almost good things, too.

For flash and aggro, try the mountain of rubbish by Tim Noble and Sue Webster, spotlit against the wall to reveal that - at its crest - the rubbish is crafted to cast the precise silhouettes of the artists themselves. Title:
The Undesirables. Or try Mauritzio Catelan's effigy of the Pope, seemingly struck down by a meteorite.

As for dull, there are the paintings of Richard Prince, their washy white surfaces, stencilled with daft stand-up jokes ("You know, I was up there in prison talking to Charlie Manson and he says to me 'Is it hot in here, or am I crazy?' "), or Wolfgang Tillmans' intensely fashionable lowcontent photos, or Darren Almond's replicas of the bus-shelters outside present-day Auschwitz.

It's not that these works are exactly about nothing. But they are so vaguely focused, they ask so much generous input from the viewer to make them interesting, that you'd have a more stimulating time just left to your own thoughts.

Art, after all, is not compulsory.

I am not sure where to place Mariko Mori's
Dream Temple. Her work generally offers spacey fusions of new technology and old spirituality. This is a Disneyesque Buddhist temple, containing a sphere into which visitors are admitted, one at a time, for a five-minute audio-visual experience. Long queues quickly gather, and you have to wait in person. Doing my best to simulate a real visit, the question was: would I, in an art gallery, queue idly for three-quarters of an hour to see one piece? And the answer was: obviously not. So I didn't. But I asked a person coming out how it was, and she said there were floating blobs, and it was like the meditation zone in the Dome, and I believed her. Whatever, you'll get a good sit down.

Hell, by Jake and Dinos Chapman, is the exhibition's big set-piece, and it almost comes off. Nine glass cases contain a miniature landscape, full of romantic chasms and swamps, occupied by an enormous and fantastical death-camp. Thousands of model figures are found torturing and slaughtering each other, with seas of tiny corpses and the dead rising to be destroyed again. It's like a video game devised by William Burroughs. It blends Nazi exterminations with medieval infernos. And when I say that the victims in this hell are all in Nazi uniform and the tormentors are naked mutants with multiple body parts, you'll see the opportunities for lively moral cacophony and inventively imagined cruelty.

If this description sounds flippant, then so, of course, is the work. It's a sci-fi, horror-movie, graphic novel phantasmagoria of modern evil, and those critics who have found in it a terrifying glimpse into the heart of 20th-century darkness seem to have missed its aspect of blasphemous farce. Still, the black joke doesn't quite work, I think because the work's model-shop aesthetic (and how much model-shop miniaturism there's been in art lately), though it's meant to up the callousness - poor little awkward, helpless figurines put through these agonies! - is so inherently inert that attention drifts. The whole thing depends on the spectacle being
fascinating. But the making of it gets in the way.

Actually, the thing I liked best was a magnification (there's been a lot of that lately too, of course): Jeff Koon's
Balloon Dog. Here, the form of a standard dog made of a twisted balloon is greatly enlarged, and cast in stainless steel, to create a beautiful Brancusi-esque object that is also replete with vulgar humour. The hardening and shininess of the surface brings out - by contrast - all the carnal and sausagey nature of the balloon, its twists and tucks and swellings, and its similarity to a condom. The belly-button puckering of the knotted mouth (it is the dog's nose) is a delightful
trouvaille. I'm sorry the piece is surrounded by some of Koons' silly pictures. The show's almost worth it just for that.

But I think Apocalypse is chiefly memorable as a phenomenon of publicity. The works inside don't matter too much. This is the art-show as style statement, employing a language now indistinguishable from that which is used to recommend a look or an aroma. Here is the ending of the curatorial essay, and the appeal is unmistakable: "We need to confront evil visually; we need to enjoy dreams; we need to be aware of the difference between reality and the virtual; we need to understand the absurdity in all things; we need to laugh; and we need to understand and be tolerant of the borders of the mind, the heart and the spirit."